Lacquered metal container for foodstuffs



Patented Sept. 17,1940

LACQUERED METAL coN'rAmEa FOB FOODSTUFFS William Clayton, London, England, assignor to Crosse and Blackwell Limited, London,-

land, a British company Eng- No Drawing. Application July 2, 1936, Serial No.

. 88,689. In Great Britain July 6, 1935 1 Claim.

The'object of. the present invention is to provide improved means for internally lacquering tin plate containers.

This invention relates to an improved process and apparatus for treating metal containers especially cans of tin plate. I

When food products are preserved in metal containers it is frequently necessary to protect the metal from attack by coating the metal with m a lacquer. This coating is usually applied before the metal sheet is formed into the can and, during the mechanical processes necessary to form the can, the lacquer film is liable to be ruptured, with consequent exposure of the metal and danger of 15 subsequent corrosion. I

According to the present invention I have found that a metal container'can be very effectively protected against corrosion by laequering the inside of the said container by depositing the lacquer electrophoretically from a lacquer-emulsion of the oil-in-water type, the deposited film being subsequently stoved if necessary.

The lacquers should be light coloured and otherwise-suitable for contact with foodstuffs, and asphaltic or pitchy emulsions are thus unsuitable.

A suitable emulsion is made from the usual ingredients employed for lacquerlng food con tainers, e. g.

so Linseed stand oil "175-200 lbs.

Synthetic res 100 lbs. Mn/Co drier (10:1 1 lb. of metal as linoleate i 40 from grease. 'When a tinplate can holding 10 fiuid ounces forms the anode, an initial current of 2 amps. gives an eifectivedeposit in about 5-10 seconds. After discharging the emulsion and washing, the can may be stoved for 30 minutes at 380 F.

The volume of the disperse phase of the emul- 5 sion may be as high as 50% and the current density may vary between wide limits, the higher the current density the greater the rate of deposition.

When using an aqueous medium which is alkaline or oxidising, the invention has an important advantage in that as a result of the electrical treatment the tinplate gains an anodic protection which is manifested in that the subsequent lacquer film no longer shows evidence of sulphide stains on the plate below. For instance, certain tinplates covered with the same lacquer, in the one instance electro-deposited and in the other with the usual mechanical rolling method, were made into cans and filled with meat rolls. After sterilisation and cooling, the cans wereopened, and whereas the can internally lacquered in the usual way showed marked sulphide staining of the plate beneath, the can lacquered electrically was entirely free from. such stain. According to the invention, it is therefore possible to employ a transparent lacquer for meat products and other foods giving on sulphur compounds, in place of the special lacquers hitherto employed containing zinc oxide or other suspended matter.

I, declare that what I claim is:

A container for foodstufis formed from tin plate, said container having the inner tin-coated surface thereof anodically treated to prevent staining, and a coating of transparent lacquer electrophoretically deposited on and covering the inner surface of said container.

CLAYTON. 4o 

